Pressurized gases for medical and other uses are normally contained in a cylinder with a dispensing valve mounted on the top. The cylinders are subject to receive bumps and impacts during transportation and handling which can damage the valve if it is not properly protected. Such cylinder valve combinations are typically configured with simple on-off valves and do not include pressure control or flow control. They lack the ability to deliver gases at desired pressures and flow rates including special applications in which approximately atmospheric pressure is desired. It is entirely important to the proper and accurate functioning of internal pumps engaged with certain air monitoring instrumentation that the valve combinations have the ability to deliver gases at approximately atmospheric pressure.